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Centrifugal fans move air radially and are better for high-pressure applications. They consist of an impeller, fan housing, drive mechanism, and blades that can be forward, backward, or radial. They are used in industrial processes, air pollution control systems, and HVAC systems.
A centrifugal fan is a fan in which the air flows radially or perpendicular to the fan shaft. This is in contrast to axial fans, the type commonly used for home cooling, where the air flows parallel to the fan shaft. While axial fans can move large volumes of air, centrifugal fans are better suited for applications that require high air pressure. For this reason centrifugal fans are used in many industrial processes and in air pollution control systems.
The parts of a centrifugal fan include the impeller, fan housing, drive mechanism, and inlet or outlet shutters. The impeller consists of fan blades mounted on a hub, which is rotated on a shaft which passes through the impeller housing. Air enters the impeller through the center of the impeller, then rotates 90° to pass over the impeller blades and exit the impeller housing.
The impeller drive mechanism can be direct, belt or variable. Which drive mechanism a centrifugal fan is equipped with determines how fast the fan moves and how much this speed can be varied. For direct drive, the fan and motor shaft are directly connected, so that the speed of the fan is equal to that of the motor shaft and cannot be varied. One or more belts are used to connect the impeller and motor shaft in a belt driven mechanism and the speed of the impeller depends on the ratio of the shaft size. Variable drive fans allow the fan speed to be varied by the use of hydraulic or magnetic couplings.
The blades of a centrifugal fan can be forward, backward or radial. The front blades are curved in the direction of rotation of the impeller, have high efficiency and can be built with small dimensions. Backward blades can be either backward curved or straight. They have high efficiency and low energy and noise requirements, and the straight-back blades are also self-cleaning. Radial blades extend directly from the fan hub, are self cleaning, and are often used in air pollution control systems because they are less sensitive to particulate buildup.
Centrifugal fans are used in many industrial processes because they are capable of producing large increases in air pressure. They are often used in grain drying and greenhouse ventilation. These are also common in air pollution control systems and heating, ventilation and air conditioning (HVAC) systems.
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